Aeration pump

ABSTRACT

A centrifugal pump for use in aerating liquids. A disc-shaped impeller is confined within a pump housing which includes an inlet port adjacent the center of the impeller and an outlet port formed in a volute chamber which surrounds the outer periphery of the impeller. The impeller is conventionally mounted on a drive shaft supported by bearings in the housing and includes radially extending, partially closed curved vanes on an outer side thereof. The impeller also includes short, radially extending auxiliary vanes on an inner side. The periphery of the impeller is notched between the vanes to substantially the depth of the closed portions of the vanes. At least one air inlet is provided in the pump housing near the outer ends of the impeller vanes to permit the injection of air under pressure for aerating the liquid being pumped.

United States Patent Warren May 16, 1972 54] AERATION PUMP 1,277,151 8/1918 Suczek ..417 72 3,217,655 11/1965 Sercy et al.... .....4l5/116 [72] lnventor. Clinton C. Warren, Vancouver, Wash. 3,226,940 H1966 Jekat et al" W45 l6 [73] Assignee: Cornell Manufacturing Company, Port- 3,462,071 8/1969 Garue ..415/1 16 land, Oreg. 3,506,373 4/1970 Danker et al. ..415/106 Filed: J 1970 FOREIGN PATENTS OR APPLlCATlONS 1 1 p 4,686 811,589 1/1937 France ..415/109 979,431 1/1965 Great Britainm. 52 us. c1 ..415/116, 261/93, 417/327, 328,851 11920 Germany 415/106 51 1 1m. 01 ..F04d 31 00, F04b 13/02 Pnmary y Raduazo 581 Field of Search ..415 1 16, 106, 1; 417/66, 72, Attorney-149118911 & Haflwe" [57] ABSTRACT [56] References cued A centrifugal pump for use in aerating liquids. A disc-shaped UNITED STATES PATENTS impeller is confined within a pump housing which includes an 1n1et port ad acent the center of the 1mpeller and an outlet 2,441,708 5/ 1948 Luaces et al ..417/13 rt fo med in a volute chamber which surrounds the outer 2,873,945 2/1959 Kuhn 15 periphery of the impeller. The impeller is conventionally 2,938,467 1 960 n rg u mounted on a drive shaft supported by bearings in the housing 3,217,655 1 Sercy Ct al. ..415/1 16 and includes radially extending, Partially closed curved vanes 3,245,656 4/1966 Desballlets et a1 ..415/169 n an outer ide thereof The impeller also includes short 2,720,836 10/ 1955 'f et radially extending auxiliary vanes on an inner side. The 1,653,189 12/1 927 p f periphery of the impeller is notched between the vanes to sub- 906332 12/1908 Huquemnm "417/72 stantially the depth of the closed portions of the vanes. At 1,009,908 1911 Lflfore 53 least one air inlet is provided in the pump housing near the 1,099,921 1914 Gibson 417/72 outer ends of the impeller vanes to permit the injection of air 1 526,596 2/1925 Greenawalt- 261/93 under pressure for aerating the liquid being pumped. 1,540,530 6/1925 Bogdanoff ..417/66 1,682,945 9/1928 Weiner et a1. ..417/71 4 Claims, 2 Drawing Figures AERATION PUMP BACKGROUND OF THE INVENTION The present invention concerns a centrifugal pump especially designed for use in aerating liquids. More particularly, the invention concerns a centrifugal pump having a novel impeller and air injection arrangement, as well an improved water seal on the inlet side of the impeller.

Aeration, as the term is used herein, refers to the dissolution of air in liquid, as opposed to the mere entrainment of air bubbles. Aeration of liquids is particularly desirable in pollution control operations. Thus, water is often aerated to freshen it prior to human usage or to destroy bacteria therein. In other applications, it is common to aerate water to facilitate the removal of oil and other pollutants which may be separated therefrom as surfacescum.

In all such applications it would be convenient to merely add the desired amount of air during a necessary pumping operation, using a conventional centrifugal pump for example. However, the addition of significant quantities of air to the inlet or eye of a centrifugal pump will cause the pump to lose outlet pressure and stop pumping.

To be more specific, the impeller of a conventional centrifugal pump comprises a circular disc having radially extending curved vanes thereon and being rotated by a shaft attached to the eye of the disc. The impeller is confined within a housing which includes an inlet port located adjacent the impeller eye and an outlet port located in a volute chamber surrounding the outer periphery of the impeller vanes. When liquid is admitted to the eye of the rotating impeller, it is picked up by the vanes and moved under centrifugal force to the volute chamber where it is expelled under high pressure. The pressure created at the outlet creates suction at the inlet port so that the pump operates without positive input pressure.

Since air is of lower density than liquid, it is not as readily influenced by the centrifugal force exerted between the impeller vanes. Consequently, any air admitted to the eye of the impeller tends to accumulate in bubble s along the inner curve of the impeller vanes. If air is continually admitted to the inlet 'portof an operating pump, the bubbles will become suffrciently large to completely block the flow of liquid between the vanes. This in turn will cause the pump to lose pressure and cease operation.

Consequently, it has been necessary in the prior art toemploy a pair of staged centrifugal pumps in aerating systems. In such systems the first pump is utilized to create positive pressure at the inlet of the second pump and thereby permit the introduction of air at the inlet of the second'pump in sufficient quantities to yield the desired level of aeration. While continuing aeration is possible with such an arrangement, the use of two pumps in a single pumping operation is clearly undesirable in that it increases both the equipment and operating costs.

SUMMARY OF THE INVENTION Accordingly, it is an object of the invention to provide an improved method and apparatus for efficiently dissolving gas in liquid materials.

It is another object of the invention to provide an improved centrifugal pump foraerating'water.

It is a further object of the invention to provide a centrifugal pump having an improved impeller and air injection arrangement.

It is yet another object of the invention to provide a centrifugal pump having an improved water seal arrangement.

These and other objects of the invention are attained by a centrifugal pump having an impeller confined within the usual housing provided with a center inlet port and an outlet port from the volute chamber. The impeller includes a plurality of curved, partially closed vanes on the outer side and is notched along its outer periphery between the vanes. The inner side of the impeller is provided with auxiliary vanes and includes two separate bearing surfaces rotatably fit with corresponding surfacesof the inner housingto define a uniquearrangement of water seals. Air isadmitted to the housing under a pressure slightly higher than the pump output pressure, at a location near the tips of the impeller vanes where it ishighly agitated to facilitate dissolution.

BRIEF DESCRIPTIONOF THE DRAWINGS Other objects and features of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevation view in cross-section of a centrifugal pump designed in accordance with the invention; and

FIG. 2 is a front elevation view in cross-section of the pump shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION,

Referring now to the drawings, a centrifugal pump is shown comprising a generally circular housing 10 having an inner wall 11 and an outer wall 12 confining an impeller 30 adapted to rotate in a counterclockwise direction as viewed in FIG. 2. Wall 12 includes an inlet port 15 located opposite the eye of the impeller. Wall 12 is formed with a circular, inner sealing ring or surface 13 and an outer sealing surface 14 oriented substantially perpendicular to the plane of rotation of the impeller.

Housing 10 further includes a volute chamber 17 generally surrounding the outer portions of the impeller and joining the outer edges of walls 1 l, 12.

As shown best in FIG. 1, the cross-sectional area of the volute increases along the periphery of the housing in a counterclockwise direction until the volute chamber terminates in an outlet port 18.

The pump housing further comprises an air inlet port 20 formed in the outer wall 12 near the outer periphery of the impeller immediately to the left of the outlet port 18. An air channel 21 communicates with the port 20 and is adapted to be connected to an air supply source 45 for delivery of air to the interior of the housing for a purpose to be explained.

Shaft 24 is rotatably supported in the center of the pump housing by a bearing 26 in a conventional manner and is adapted to be driven by suitable motive means, not shown. Hub 3] of impeller 30 is secured for rotation with shaft 24 by a washer 28 under the force of cap screw 29. Water tight seals are-provided on the shaft, adjacent the hub in a conventional fashion. Impeller 30 includes an inner side 32 having auxiliary vanes 33 thereon, as shown in dotted outline in FIG. 2; and an outer side 34 having a set of main vanes 35 thereon which comprise the working elements of the pump. The vanes are, of generally elongate, curved form extending from the eye of the impeller to its outer periphery. Vanes 35 include open outer portions 38 and closed inner portions 36 which cooperate to form liquid passages 37 from the pump inlet to the volute 'chamber. The closed vane portions include a circularinner seal surface 39 and a similar outer seal surface 40, adapted to rotatably fit with surfaces '13, 14 respectively, of the housing wall to form a unique arrangement of water seals. The outer periphery of the impeller is formed with relatively deep, curved notches 42 between the main vanes. As shown best in FIG. 2 the notches extend inwardly substantially the entire length of the open vane portions to define tooth-like segments along the outer periphery of the impeller for a purpose to be explained.

In operation the pump impeller is rotated so that liquidadmitted to the inlet port is confined between the main vanes and moved outwardly under centrifugal forceand increasing pressure to the volute chamber 17. Since the the velocity of liquid leaving thevanes decreases, the volute pressure increases andthe liquid is expelled from the outlet port at a high outlet pressure. The force of the expelled liquid creates suction at the pump inlet port so that the pump will operate satisfactorily without positive inlet pressure.

Since the pressure in channels 37 opposite seal surfaces 14, 40 exceeds the inlet pressure, a small volume of liquid is forced between those surfaces and between surfaces 13, 39 toward the inlet. This enhances pump efficiency by creating an efi'ective water seal which prevents positive air by-pass around the impeller. The auxiliary vanes on the impeller serve to create a relatively positive pressure away from the shaft and create a liquid bearing between the inner impeller surface and the housing surface.

With the pump operating and the outlet pressure at rated value, air is selectively admitted from a source 45 through air channel 21 and port 20 to the interior of the housing. As shown, the air is injected near the tips of the vanes and is thoroughly mixed with liquid during an entire revolution of the impeller before being expelled through the outlet port. As best seen from FIG. 2, the movement of the impeller creates circulation patterns in the liquid about the tips of the vanes resulting in extreme agitation of the liquid and air mixture whereby large quantities of air are dissolved.

It should be apparent that an air inlet pressure is required which slightly exceeds the pump outlet pressure. The volume of air admitted may be controlled by suitable means, not shown, to achieve the desired levels of aeration.

In a typical cycle of operation a centrifugal pump having a 12-inch impeller and being powered by a 25 horsepower motor produced a flow of approximately 200 gallons per minute of water at 55 F. with an outlet pressure of 50 psi and no positive inlet pressure. Under the above conditions, an air flow of 4 to 5 cfm into the pump housing resulted in the dissolution of approximately 1.4 scfm of air into the fluid. The above results are highly satisfactory in terms of the theoretical dissolution and significantly better than other results attained in the prior art.

While the preferred embodiment of the invention has been explained as being used for the aeration of water, it should be apparent thatthe centrifugal pump of the invention may be used to dissolve any suitable gas within selected liquids or mixtures of liquids.

it is claimed:

1. A method of conditioning a liquid by dissolving gas in said liquid comprising the steps of:

continuously introducing quantities of said liquid through an inlet port into an annular chamber;

continuously forcing quantities of said liquid to a confined outer portion of the annular chamber to raise the liquid pressure in said confined outer portion to a predetermined level;

continuously injecting quantities of pressurized gas into the chamber proximate the confined outer portion of said annular chamber, said gas being injected at a pressure level in excess of said predetermined level; mixing said liquid and gas under pressure by moving open sided vanes through said chamber adjacent the point at which said gas is injected thus agitating said quantities of gas and liquid to facilitate solution of gas in said liquid;

and continuously expelling quantities of conditioned liquid from the confined portion of the chamber through an outlet port in the chamber at the predetermined pressure level.

2. A centrifugal pump for dissolution of gas into a liquid comprising:

a circular housing having first and second spaced apart walls joined at their outer edges by a volute chamber;

inlet port means formed in the center of said first wall for admitting liquid to said housing;

outlet port means formed in said volute chamber for exhausting liquid from said housing;

an impeller rotatably supported within said housing comprising a circular plate having an inner eye portion defined thereon, upstanding curved vanes secured to said plate extending between said eye portion and the outer periphery of said plate to define liquid channels between said vanes, and means secured to the upstanding edges of said vanes to cover said channels only within an inner portion of said impeller surrounding said eye portion, said plate having contoured notches formed in the outer periphery thereof between adjacent vanes;

and second inlet port means formed in said housing opposite the notches in said plate for admitting gas to said housing simultaneously with the liquid admitted through said first inlet port means.

3. A centrifugal pump as described in claim 2, wherein said notches extend inwardly substantially the full length of the uncovered portions of said vanes for thoroughly mixing gas injected through said second inlet port means, with liquid flowing through said channels.

4. A centrifugal pump including a rotatable impeller having an eye portion and vanes extending radially from said eye portion, said impeller having notches formed therein between adjacent vanes; and

a housing confining said impeller, said housing having a fluid inlet at the eye portion thereof, and an air injection means therein positioned radially outwardly from said eye portion proximate the path of said notches for injecting air into the path of the portions of said impeller defining said notches. 

1. A method of conditioning a liquid by dissolving gas in said liquid comprising the steps of: continuously introducing quantities of said liquid through an inlet port into an annular chamber; continuously forcing quantities of said liquid to a confined outer portion of the annular chamber to raise the liquid pressure in said confined outer portion to a predetermined level; continuously injecting quantities of pressurized gas into the chamber proximate the confined outer portion of said annular chamber, said gas being injected at a pressure level in excess of said predetermined level; mixing said liquid and gas under pressure by moving open sided vanes through said chamber adjacent the point at which said gas is injected thus agitating said quantities of gas and liquid to facilitate solution of gas in said liquid; and continuously expelling quantities of conditioned liquid from the confined portion of the chamber through an outlet port in the chamber at the predetermined pressure level.
 2. A centrifugal pump for dissolution of gas into a liquid comprising: a circular housing having first and second spaced apart walls joined at their outer edges by a volute chamber; inlet port means formed in the center of said first wall for admitting liquid to said housing; outlet port means formed in said volute chamber for exhausting liquid from said housing; an impeller rotatably supported within said housing comprising a circular plate having an inner eye portion defined thereon, upstanding curved vanes secured to said plate extending between said eye portion and the outer periphery of said plate to define liquid channels between said vanes, and means secured to the upstanding edges of said vanes to cover said channels only within an inner portion of said impeller surrounding said eye portion, said plate having contoured notches formed in the outer periphery thereof between adjacent vanes; and second inlet port means formed in said housing opposite the notches in said plate for admitting gas to said housing simultaneously with the liquid admitted through said first inlet port means.
 3. A centrifugal pump as described in claim 2, wherein said notches extend inwardly substantially the full length of the uncovered portions of said vanes for thoroughly mixing gas injected through said second inlet port means, with liquid flowing through said channels.
 4. A centrifugal pump including a rotatable impeller having an eye portion and vanes extending radially from said eye portion, said impeller having notches formed therein between adjacent vanes; and a housing confining said impeller, said housing having a fluid inlet at the eye portion thereof, and an air injection means therein positioned radially outwardly from said eye portion proximate the path of said notches for injecting air into the path of the portions of said impeller defining said notches. 